HE (hematoxylin-eosin) stain uses hematoxylin and eosin as a dye, and is widely used in the field of histology for observing tissue sections. Among them, hematoxylin is a blue-violet dye, and has a property of staining basophilic tissues such as cell nuclei, bone tissues, part of cartilage tissues, and serous components. Eosin, on the other hand, is a red to pink dye, and has a property of staining eosinophilic tissues such as cytoplasm, connective tissues of the soft tissue, red blood cells, fibrin, and endocrine granules. Due to such properties of hematoxylin and eosin, HE stain is widely used to obtain morphological information on tissue specimens.
On the other hand, immunohistochemistry (IHC) is widely known as a histological (histochemical) tool for detecting an antigen in a tissue specimen using an antibody. The immunohistochemistry may be referred to as “immunological staining” due to the process of color development for visualizing an antigen-antibody reaction which is otherwise invisible (hereinafter, the term “immunohistochemical staining” may be used for immunohistochemistry). Due to the characteristics of visualizing the location of an antigen-antibody reaction, immunohistochemistry is widely used in the fields of medicine and life chemistry for the purpose of detecting a location of a biological substance in a tissue specimen.
As a histological (histochemical) technique related to immunohistochemistry, lectin staining is also known. The lectin staining is a technique that utilizes a property of lectin of binding to a specific sugar chain in a non-immunological and specific manner in order to detect a sugar chain in a tissue specimen using lectin, and is widely used in fields related to sugar chains.
All of the HE staining, immunohistochemistry and lectin staining are used as methods for detecting a location of cancer cells in a cell specimen. For example, when it is desired to confirm a location of cancer cells in a cell specimen, a pathologist, in order to determine the presence or absence of cancer cells in the cell specimen, conventionally prepared a plurality of tissue sections (hereinafter referred to as “sections”) from a tissue specimen; subjected a first section to HE staining in order to obtain its morphological information, and determined the presence or absence of cancer cells; and prepared, by use of a second section, a dye-deposited section by an enzymatic reaction and determined the presence or absence of target molecules. While there were cases where, instead of immunohistochemistry, lectin staining was used in conjunction with HE staining, similar procedures were used therein. For diseases other than cancer as well, similar procedures were generally used in detecting the focus of a disease in a cell sample with HE staining and immunohistochemistry (or lectin staining). The observation of an identical site with two sections requires a lot of work and expertise, which caused a source for variation in pathological diagnosis. Under such circumstances, methods have been tested that attempt to determine the presence or absence of a target molecule by binding a fluorescent body such as a fluorescent dye or semiconductor nanoparticles (quantum dots) to antibody. However, these methods have problems that such a fluorescent body can only emit a small amount of fluorescence. Thus, proper separation and removal of autofluorescence resulting from the section per se were prerequisite in order to determine a location of the target molecule based on fluorescence from the fluorescent body, and in addition the HE staining of another section was still necessary to obtain morphological information.